When using a hand operated drill motor to drill a hole in a work piece, the operator presses against the handle of the drill motor to push the drill against the work piece. This is easy and safe to do when the work piece is below the operator and the operator can use his body weight as the source of the forward force. If the work piece is on a vertical surface such as a wall, the operator leans into the drill bit again using his body weight as the source of the forward force. However, if the operator is on a ladder and has to push against a wall, the operator and ladder tend to move backward possibly causing a dangerous condition. An overhead work piece requires the operator to use the muscles in his arms to push the drill up.
If the work piece can be moved to the drill, a drill press is ideal for drilling the hole. A table supports the work piece and a drill is forced into the work piece with the aid of a lever.
A drill press head having an electromagnetic base is available for work on steel construction. The electromagnet takes the place of the table and base of a regular drill press. When the operator wants to drill a hole in a large steel member, he moves the unit to the desired location and turns on the electromagnet which clamps the unit to the work piece. The head is then operated in the same manner as a drill press head to create the hole. When he is finished, the operator turns off the electromagnet which releases the unit from the work piece. This type of unit tends to be large and expensive and is useful only for steel construction.
Smaller hand drill press arrangements have been developed. U.S. Pat. No. 4,576,529 to Forrer shows a drill motor mounted on a bar for drilling a work piece held against a jaw member. Forward force for drilling is provided by a threaded spindle engaging a threaded aperture and rotated using a crank handle. The operator holds the drill motor with one hand while rotating the crank handle with the other. Rotation of the spindle with the crank is awkward, however, and tends to throw the drill to the side out of alignment with respect to a fixed work piece.
U.S. Pat. No. 4,860,735 to Davey et al. illustrates a guide for drilling along a line with a drill motor during surgery but does not have a forward moving means.
U.S. Pat. No. 5,314,271 to Christiano shows a portable drill guide based on a welder clamp type locking plier such as sold under the trademark VISE GRIP.RTM.. It is primarily used for drilling out spot welds in sheet metal. The drill motor is mounted on one of the jaws perpendicular to the opposite jaw. A work piece is drilled between the end of the drill and the opposite jaw while the operator squeezes the locking plier handles with one hand and holds the drill motor with the other. The thickness of the work piece is seriously limited.
U.S. Pat. No. 5,322,397 to Spear shows a stand for drilling overhead. The stand is jacked between a floor and the overhead work piece. The drill motor on the stand is pushed into the overhead work piece using a lever.
All of the devices shown in the referenced patents are difficult to use or are useful only in limited circumstances. A hand drill press that could be operated by one hand while the operator uses his other hand to hold the work piece or himself would be an improvement.
Slide bar clamps sold under the trademark QUICK-GRIP.RTM. by Peterson Manufacturing Co., Inc. of DeWitt, Nebr., provide linear clamping force along a slide bar between a moving jaw held by one hand and a fixed jaw as shown in U.S. Utility Pat. Nos. 4,926,722; 5,009,134; and 5,022,137, and U.S. Design Pat. No. 320,919. As the operator repeatedly squeezes the trigger on the movable jaw, the movable jaw walks along the slide bar in a linear fashion toward the fixed jaw. Each squeezing of the trigger moves the movable jaw only slightly forward translating the gripping force of the hand into significant forward force due to the leverage provided by the trigger mechanism. The operator can readily determine the amount of clamping force applied between the movable jaw and the fixed jaw by how hard he squeezes the trigger.
QUICK-GRIP.RTM. clamps are sold to clamp work pieces for gluing and assembly. A significant advantage of QUICK-GRIP.RTM. clamps over other clamps is that they can be operated entirely by one hand while the operator uses his other hand to control the work piece. Most other portable clamps require two hands to operate. Another significant advantage is that the force applied by the clamps is always linear between their movable jaws and fixed jaws. Other clamps usually are applied using torque which tends to throw them to the side or rotate them during application. No suggestion is made for any method of using such slide bar clamps with drill motors.